Selective agent for concentrating ores



Patented Feb. 17, 1931 UNITED STATES PATENT OFFICE SELECTIVE AGENT FOR CONCENTRATING ORES No Drawing.

The present invention relates to the concentration of ore, in the act of which, the valuable mineral contents is separated from the earthy or rocky content commonly called 5 gangue. More particularly, the invention embodies an improved compound for accomplishing the concentration more effectively.

In practicing the invention, advantage is taken of the known preferential affinity of certain substances for certain minerals, over other minerals and substances which, in the present refining methods are discarded as valueless. It is found that certain compounds of these selective substances not only attract the nobler metals, such as gold, silver and platinum, but repel the gangue content of the ore which is usually composed of silicious compounds or compounds of iron.

Present methods employ mercury or quick silver on amalgam plates and it is an object of this invention to provide an improved. method whereby the valuable metals may be separated from the ore far more effectively and economically than previously accomplished by any known method.

More particularly, the invention relates-to What is generally known as the contact meth- 0d of ore concentration, in which the ore, in a finely divided state, is mixed with water to form a pulp. This pulp is then brought into contact with a surface to which the valuable mineral content only of the ore will adhere. A further object of the invention, therefore, is to provide a more powerful selective agent than now known, which not only has a great affinity for a few of the precious metals, but for practically all of the baser metals, including their oxides and carbonates. 7 As an additional feature, this agent repels the gangue, thus effectively separating and concentrating the ore.

It is proposed to utilize, in connection with the invention, an apparatus having an endless belt which is agitated in any suitable 45 manner, one type of such device being de- Serial No. 322,588.

scribed in the patent to Luckenbach N 0. 1,448,928, dated March 20, 1923.

In carrying out the invention a selective material is used which attracts the metals to be concentrated and repels the gangue and waste material. Metals are, by nature, greasy. Since like substances attract like, a tar or grease of an oleate nature is used to attract the precious metals. This ingredient, at the same time repels water and gangue.

The preferred selective material utilizes for the above element, candle tar, which is an animal substance, although any animal, vegetable or mineral oil, tar or grease of an oleate nature may be used it found suitable commercially. Candle tar is a recognized residue formed in the manufacture of candles. To soften the candle tar, crude petroleum is preferably used, this substance also selecting the minerals and repelling water and gangue. If a substance other than candle tar is used which is not too hard and does not require softening, the crude petroleum may be eliminated. *Any oil or tar. of a paraflin or asphaltum base including any liquid petroleum or any animal, vegetable or mineral oil found :gQsuitable commercially may be substituted for the crude petroleum. For example, coal tar, which is of a vegetable base, has been found quite suitable as a substitute for the crude 7 petroleum.

The other ingredient of the selective substance is silicate of soda which repels gangue and iron. This substance forms a film over the gangue and iron to enable them to become wet very rapidly. When wet, the gangue and iron will not adhere to the grease or oil but. on the contrary, arc repelled by them. The silicate of soda does not affect other minerals unless uscdin excess.

Any mineral compound of an alkaline base, such as silicate gel, aluminum soap, caustic soda, potash. (the last two being mixed with candle tar), may be used in place of silicate of soda. The silicate of a liquid or jcllied base must have a very water repellant nature and the particular mineral compound of an alkaline base used may be governed by commercial factors. If desired the compound may be used without the silicate which may be availed of by treating the water with it.

The proportions of the ingredients of the selective material to give the best results has been found to be three parts of candle tar by weight, one part of petroleum, and one part of silicate of soda. This compound is placed in the form of a thin coating upon the surface of a continuously moving belt, the application of the compound to the belt preferably being accomplished automatically during the operation and its removal effected by a suitable scraper beneath the belt.

By reason of the weight and coarseness of the mineral, the latter goes down instead of floating. In this respect, the invention is the reverse of the oil flotation agent. The improved method possesses a great advantage over the oil flotation method in that it is capable of use with coarse ores, the latter method requiring the ore to be ground to 80 or 100 meIh while the improved method described herein requires the ore to be ground only to 30 mesh.

The improved, or contact method, requires very little power for operation, a great saving being effected in the grinding operation. The method is continuous and may be practiced entirely automatically. In addition, the selective agent may be recovered by means of a filter press and used indefinitely, thus affording another great advantage over the oil flotation method in which the oil can only be recovered with great difliculty.

Metals in the free or virgin state as well as certain chemical combinations thereof, including metallic minerals and their sulphides are effectively separated from the earthy gangue with which they are associated. Nonmetallicminerals such, for example, as sulphur and graphite may likewise be concentrated. Whether the ores have a fiinty or rocky gangue, or the metal is in a free state such as in placer or surface mining, the invention is equally effective.

It will be apparent that the invention may be carried out with all ores and their chemical compounds which are subject to concentration by the oil flotation methods in common use as well as with other mineral substances ;iot affected by the materials employed in the oil flotation processes in common use. In addition to the specific compound described, these minerals have been recovered by selective compounds, the ingredients of which have included oils or tars of paraflin or asphaltum bases as well as coal tar, of a vegetable base. For example, crater oil and horse rease, tallow or lard oil have been used with great success.

It is obvious that the invention may emand varied body selective materials of many d imite ,save 

